(1) Field of the Invention
The present invention relates to a transfer device and an image forming apparatus including this device, in particular, relating to a transfer device including a detecting mechanism for detecting replacement of a new unit.
(2) Description of the Prior Art
An electric appliance such as a color image forming apparatus etc., includes a sensor for detecting a new unit being set, in order to determine the time of replacement of a removable unit. The appliance also includes a sensor for detecting whether the replacement unit is correctly attached inside the appliance.
In the above way, there is the need for providing a plurality of sensors for detecting the information on attachment of a replacement unit, posing the problem of increasing the production cost and reducing reliability.
To deal with the above situation, there is a disclosure (patent document 1: Japanese Patent Application Laid-open Hei 05 No. 204195) of a photoreceptor unit of an image forming apparatus, in which, in order to reduce the number of the sensors as above, a common sensor is used to detect both the presence of the unit and whether the unit is new.
However, a transfer device for a color image forming apparatus, for example, needs many sensors other than the aforementioned sensors, including sensors for determining the operational status such as color mode, monochrome mode, non-printing mode or the like. Therefore, it has been difficult to obtain better results in cutting down the production cost and improving reliability by only integrating the sensor for detecting the presence of a unit with that for detecting whether the unit is new and old into a common configuration.